The present invention relates to a new and improved arrangement for controlling a controlled deflection roll.
Generally speaking, there is contemplated an arrangement for controlling the pressing force between a counter element and a controlled deflection roll, wherein the roll shell of such controlled deflection roll can be pressed by force-applying sources against the counter element. These force-applying sources are arranged in a distributed fashion in the axial direction of the roll shell and are supported upon a roll support or beam. In each case groups of force-applying sources can be separately controlled, and there is provided a common adjustment or setting element for a desired pressing force for generating a common control signal. This control signal is converted by converters correlated to a respective group of force-applying sources into group control signals in such a manner that at the range of the pressing forces which are to be adjusted there can be minimized the deviations from a pressing force-mean value lengthwise of the controlled deflection roll. The group control signals can be influenced by externally generated correction signals. An arrangement of this type is disclosed in the commonly assigned, copending U.S. application Ser. No. 334,642, filed Dec. 28, 1981.
The possibility of being able, in principle, to work with the same mean line force, but however being able to undertake corrections at zones, enables compensating errors in the material web which is being processed. These errors are for instance caused by machines arranged forwardly or upstream of the roll system or could be caused by downstream or subsequently arranged machines. Such irregularities of the material web otherwise would also not be compensated after the roll nip when working with a pressing force which is essentially constant along the roll width. The machine operator can however monitor the rolled product and eliminate such irregularities by individually adjusting the pressing force. As an alternative approach it would also be possible to measure the properties of the material web following the roll nip and to feed back appropriate correction signals to the converters, as such has been disclosed in German Patent Publication No. 2,555,677 and in the cognate U.S. Pat. No. 4,074,624, issued to Biornstad et al on Feb. 21, 1978.
Supporting of the roll shell upon the force-applying sources arranged in an offset fashion in axial direction, that is to say, engaging or acting to a certain extent "locally" at the roll shell, presupposes that the roll shell possesses sufficient rigidity or stiffness in order to bridge the so-to-speak "gaps" between the individual points of application or attack of the force-applying sources. On the other hand, this means however that, when influencing a certain zone of the roll nip by means of a correction signal for the related group of force-applying sources at least also the neighbouring zones are adjusted or altered in the same sense, if even to a lesser degree. In an extreme case the situation can then arise that instead of attaining the desired result as to the quality of the rolled stock or product there is, in fact, produced an entirely different course or characteristic of the profile of the rolled stock. That obviously is highly undesirable because the machine operator can no longer recognize any unambiguous correlation between the settings undertaken by him or her and the end result.